Method of securing heat insulating and exothermic slabs to the inner walls of an ingot mould head



United States Patent cc 3,539,413 METHOD OF SECURING HEAT INSULATING ANDEXOTHERMIC SLABS TO THE INNER WALLS OF AN INGOT MOULD HEAD KennethThomas Eccleston, Nechells, England, assignor to Foseco Trading A.G.,Chur, Switzerland, a Swiss company No Drawing. Filed June 12, 1967, Ser.No. 645,466 Claims priority, application Great Britain, June 24, 1966,28,460/ 66 Int. Cl. C093 5/06 US. Cl. l56321 6 Claims ABSTRACT OF THEDISCLOSURE Slabs of heat insulating or exothermic material to be used toline the head of an ingot mould are provided, on the mould wallcontacting face, with a layer which includes a heat-settable adhesiveresin, The slab may be stuck easily to the ingot mould wall anddifficulties of lining ingot moulds with such slabs are thus reduced.

This invention relates to a method of assembling hot tops for ingotmoulds from a plurality of slabs of heatinsulating and/or exothermiccompositions.

It is well known practice to provide at the head of an ingot mould alining which will have the effect of delaying the rate of cooling of thehead metal, thus ensuring a continuous feed of molten metal to the mainbody of the ingot to compensate for its shrinkage as it cools.

A very large number of methods of constructing such hot tops have beendescribed. One basic method is to provide a plurality of slabs which arefitted together in some fashion against the walls of the ingot mould inorder to constitute a complete lining to the head of the ingot mould,such slabs being of heat insulating material (thus providing a barrierto loss of heat from the molten metal in the head) or of exothermicmaterial (i.e. material which fires on contact with the molten metal togenerate heat) and thus either prevent flow of heat from the moltenmetal or to add heat to the molten metal in the head, e.g. analuminothermie composition may be employed for this purpose. It hasfurther been proposed to provide such slabs which have a layer ofexothermic material to face the molten metal and a backing layer of aheat-insulating material.

The actual operation of assembling such slabs to constitute a completelining is one of considerable difficulty, especially when the ingot headopening is of large dimensions and more especially when the ingot is ofthe wideend-down construction, when the inner Walls of the mould taperoutwardly in a downward direction. It is also difficult to arrange suchslabs at varying heights in the mould to obtain varied chill lengths inthe cast ingot.

Thus, a plurality of slabs being employed to make up the lining, it isnecessary to hold all of the slabs, except that last inserted, in sometemporary position, e.g. by clamps in approximately their desiredposition, the last inserted slab serving to lock the assembly togetherand permit removal of such temporary holding devices. A commonlyemployed construction, for example, where the ingot head opening isrectangular in cross section is to employ slabs which have wedging sidesurfaces; one such slab is located on each of the four walls and thecorner slabs are inserted which make wedging action with the wall slabs.It will be appreciated that in this construction the assembly acquiresno coherence as a lining until the last corner slab is inserted, thuswedging the whole assembly tightly into position as a lining against theWalls of the mould.

3,539,413 Patented Nov. 10, 1970 In our British specification No.1,018,896 there is claimed a method of assembling a lining to the headof an ingot mould from a plurality of interfitting slabs, whichcomprises locating the slabs successively in their desired positions andproviding, in respect of all the slabs, or in respect of some or all ofthose located in position before the assembly is complete, an adhesivelayer between the slab and the mould wall, the said adhesive being anon-refractory plastic adhesive adapted to set sufficiently to hold theslab in position but not to set so firmly as to prevent a small degreeof movement of the slab relative to the mould walls without loss ofadhesion of the slab to the mould wall.

Asuitable adhesive described for the foregoing purpose is a pressuresensitive adhesive based on polyisobutylene.

The foregoing method is of limited application in that the adhesive doesnot of itself contribute to the fixing of the slabs, but merely holdsthem sufficiently while they are being assembled and fixed by some otherprocedure, e.g. by the provision of wedging pieces. It is an object ofthe present invention to provide an improved solution to the problem offixing slabs to construct a lining to the head of an ingot mould.

According to the present invention there is provided a method ofsecuring slabs of heat-insulating and/ or exothermic material to theinner walls of the head of an ingot mould which comprises applying to atleast part of the faces of the slabs which are to contact the walls alayer comprising a heat-settable adhesive resin, locating the coatedslabs in the desired positions and heating them to cause the adhesiveresin to melt, bond to the wall of the ingot mould and set to form arigid bond.

The heating of the slabs may conveniently be effected by residual heatin the ingot mould itself. The invention further includes slabs ofheat-insulating and/or exothermic material having on at least part ofthe face of the slab which is to contact the ingot mould walls a layercomprising a heat-settable adhesive resin.

In one form of the invention the heat-settable adhesive resin is in theform of fusible particles, suspended in a viscous liquid medium, andaccording, therefore, to a specific feature of the invention, there isprovided a method of securing slabs of heat-insulating and/or exothermicmaterial to the inner walls of the head of an ingot mould whichcomprises applying to the faces of the slabs which are to contact thewalls a layer comprising a particulate fusible, heat-settable adhesiveresin in a viscous liquid medium, locating the coated slabs in thedesired positions and heating them to cause the adhesive resin to melt,bond to the wall of the ingot mould and set to form a rigid bond.

The invention further includes slabs of heat-insulating and/ orexothermic material having a coating thereon of a composition comprisinga particulate fusible, heatsettable adhesive resin in a viscous liquidmedium. Such slabs may differ in the nature of the viscous liquid mediumaccording to the manner in which they are to be used. Where the slabsare intended to be applied to a cold mold it is important that theviscous liquid medium should have some adhesive properties to hold theslabs in position up to the time when the mould is heated by the pouringinto it of molten metal. In this case, it is preferred that the mediumshould be an adhesive of the type described in British patentspecification No. 1,018,896, e.g. a pressure sensitive adhesive,preferably one based on polyisobutylene. Where, however, the slabs areintended to be applied to a hot mold it is not necessary to provide sucha temporary adhesive since on contact with the hot mould Wall theheat-settable particulate fusible adhesive resin will melt, bond and setrigid.

In this case the viscous liquid medium may be for example a natural gumsolution, e.g. of gum arabic or gelatin.

In either event the presence of the particulate heatsettable resin tendsto reduce the overall tackiness of the coating so that it is possible,within the scope of the invention, to provide slabs with coatings of solow a tackiness that it is not necessary to provide a protective layerover the coating as is necessary for the coated slabs of British patentspecification No. 1,018,896 to facilitate their handling and transport.

The heat-settable resin may be of any type. Particularly good resultshave been obtained by the use of phenolformaldehyde resins.

The coating containing the heat-settable resin need not extend over thewhole face of the slabs which is to be juxtaposed to the mould wall. Itis sufiicient to provide a coating the form of strips or a grid, orisolated patches but preferably the coating is present at least near tothe margin of the slab. The bond made by the resin between the slab andthe mould wall should be sufficiently strong to prevent liquid metalentering between the slabs and the mould wall, i.e. suificient toprevent floating" of the slabs.

The quantity of heat-settable resin is, of course, selected havingregard to its bonding properties and the weight of the slab which it isto support.

Further heat-settable resins of use in the present invention arearrested epoxy resins. Arrested epoxy resins are formed by mixing theepoxy resin and hardener together, usually with a quantity of filler,and subsequently cooling the pasty composition formed. The materialsubsequently forms a tacky composition which slowly turns hard andbrittle. This arrested epoxy resin may be melted by heating to about 70C. or over and when so heated thermosets.

In the present invention, the epoxy resin and hardener are preferablyheated to 80-100 C. and then mixed together with a filler. The resultingpasty composition is then extruded into a cold water-bath to formribbons of tacky material. This tacky material may be stuck directly tothe appropriate face of the slab, Where it adheres and subsequentlyturns brittle.

If the ribbon is allowed to become brittle prior to aflixing to theslab, the ribbon may be spot-welded to the slab. The arrested epoxyresin composition preferably contains a proportion, generally up to of afibrous material such as asbestos, glass-fibre or cotton, to minimisethe risk of breaking, cracking or flaking off of the arrested epoxyresin when it turns brittle. The amount of filler used, which may be forexample, silica flour, sand or fly ash is preferably up to 80% by weightof the composition.

Preferred resins are those consisting of a pre-condensate ofepichlorohydrin and bisphenol A, the hardener of choice beingdiaminodiphenylmethane.

Since the arrested epoxy resin in its brittle state must be heated to atleast about 70 C. before melting and consequent tackiness takes place,slabs having only a coating or strips of arrested epoxy thereupon areonly useful in hot ingot moulds. When it is desired to use such slabs incold moulds, a low-temperature adhesive must also be present. Thepreferred adhesive for this purpose is one based on polyisobutylene, asdescribed, for example, in British Pat. No. 1,018,896.

The present invention includes the method hereinbefore set forth, coatedslabs as herein described and ingot moulds having the head lined withslabs by the method herein described.

The following examples in which all parts and percentages are by weightwill serve to illustrate the invention:

EXAMPLE 1 There is applied to the surface of slabs of heat-insulatingmaterial a coating of a composition comprising equal parts by weight ofpowdered phenol-formaldehyde heatsettable resin and liquidphenol-formaldehyde resin. The slabs are applied to the cold walls ofthe head of an ingot mould. On heating, the composition sets to a hardinfusible solid bonding the slabs to the mould wall.

EXAMPLE 2 There is applied to the surface of slabs of heat-insulatingmaterial a coating of a composition comprising equal parts by weight ofpowdered phenol-formaldehyde heatsettable resin and isopropyl alcohol.The applied composition is dried down at 7080 C. This prevents the slabsfrom sticking together but without impairing the adhesive properties ofthe composition to a hot mould wall.

The coated slabs are applied with the coated sides towards the walls ofthe head of an ingot mould which is at a temperature of 15 0400 C. Thecomposition rapidly hardens and sets, bonding the slabs to the mouldwall.

EXAMPLE 3 Ground epoxy resin particles were dispersed in a 2% aqueoussolution of gelatin and the resulting viscous liquid applied to heatinsulating slabs in strips 2.5 cm. wide x 5 mm. thick. These slabs weresuitable for application to moulds at temperatures from 70 to 400 C.

EXAMPLE 4 Ground epoxy resin particles were dispersed in polyisobutyleneto give a composition of pasty consistency. Strips of this composition2.5 cm. wide by 5 mm. thick adhered strongly to slabs of heat insulatingmaterial. Slabs having such strips adhering on one side were usable inmoulds at any temperature from room temperature up to about 400 C.

EXAMPLE 5 A mixture was made up of:

Parts Epoxy resin (Epikote 828XAShell Chemicals Ltd.) Silica flour 285and to this was subsequently added 27 parts of diaminodiphenylmethane(Hardener B.250BASF). The resulting paste was extruded in ribbon formthrough a cold water bath and subsequently cut into strips which, whentacky, were applied to the surfaces of slabs. These slabs could be usedimmediately on hot or cold ingot moulds or, if the resin were allowed tobecome brittle, only on moulds above about 70 C.

I claim as my invention:

1. In a method of securing slabs of heat-insulating and exothermicmaterial to the inner walls of the head of an ingot mould, the steps ofapplying to at least part of the faces of the slabs which are to contactthe walls a layer comprising a heat-settable adhesive resin, applyingthe coated slabs to said walls in the desired positions with the coatedfaces of the slabs in contact with said walls, and heating said walls tocause the adhesive resin to melt, bond to the wall of the ingot mouldand set to form a rigid bond between said slabs and said walls.

2. A method according to claim 1 wherein the heating of the slabs iseffected by residual heat present in the mould walls.

3. A method according to claim 1 wherein the heatsettable adhesive resinis selected from the group consisting of phenol-formaldehyde resins andepoxy resins.

4. A method according to claim 1 wherein the heatsettable resin isapplied to the slab in the form of a dispersion of the resin in apressure-sensitive adhesive.

5. A method according to claim 1 wherein the heatsettable resin isapplied to the slab in the form of a dispersion of the resin in aviscous liquid medium.

6. In a method of securing slabs of heat-insulating and exothermicmaterial to the inner Walls of the head of an ingot mould the steps ofapplying to the faces of the slabs which are to contact the Walls alayer comprising a particulate fusible, heat-settable adhesive resin ina viscous liquid medium, applying the coated slabs to said 5 melt, bondto the wall of the ingot mould and set to form 10 a rigid bond betweensaid slabs and said walls.

References Cited UNITED STATES PATENTS 10/1953 Heintz 1566O 12/1965Gaston et a1 156291 X US. Cl. X.R. 156330, 335

